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  <script>
    var tel = '134567899988'
    var n = tel.slice(0, 3)
    var m = tel.slice(8)
    console.log(n + "****" + m);
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  <script>
    var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    // var total = arr.reduce((sum, item) => sum + item, 0)
    // console.log(total);
    function dg (n) {
      if (n <= 1) return 1
      return dg(n - 1) + n
    }
    console.log(dg(10));
  </script>

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